When making-up or joining a threaded tubular connection, the drilling operator needs to access the quality of the resulting connection during or immediately after make-up to reduce the likelihood of placing an improperly made-up connection in the well. A reliable threaded connection with both sealing and structural integrity is required to practically conduct oilfield operations, and hundreds of ideas have been proposal for safely, efficiently, and reliably verifying the quality of an oilfield tubular connection during make-up.
A primary tool used to determine the quality of an oilfield tubular threaded connection is the torque between the tubular segments measured during the made-up operation. The degree and uniformity of torque generated when making-up a connection is most commonly used to predict the reliability of the connection. Various U.S. patents describe techniques aimed at evaluating the resulting quality of joined components based on torque measurements. Other variables that may be monitored include strain and/or stress at or near the joint.
U.S. Pat. No. 4,957,002 discloses for determining the quality of assembly of tool parts, wherein a first tool part is assembled with a second tool part by rotatably inserting the first tool part into the second tool part to form a joint. The method comprises the steps of (a) measuring at least one of the rates of rotation of the first and second tool parts and the torque imposed on the first and second tool parts to obtain a first set of data; (b) measuring at least two of axial strain, torsional strain, and hoop strain imposed on the joint to obtain a second set of data, and (c) processing the first and second sets of data to determine the quality of assembly of the tool parts.
U.S. Pat. No. 4,791,816 discloses a device for determining when a threaded joint for steel tubes is properly made-up. The device comprises a strain gauge and means for applying said gauge on an external surface near the joint for measuring longitudinal deformations of extension or contraction on the external surface.
A technique for more generally analyzing deformations is disclosed in U.S. Pat. No. 5,042,164. A sensing device and an analysis process are used for determining the shape of the periphery of a cross-section of a body as it deforms over time. The sensing device includes a band attached to the surface of the deformable body along the external peripheral path of the desired geometrical cross-section. The band has sensing devices on it, each of which produces an output proportional to local curvature as the band is deformed. The analysis process integrates the outputs from the sensing devices to calculate the shape of the periphery of a cross-section of the body to which the band is attached.
Another system for determining the quality a tubular connection during makeup of successive sections of pipe is disclosed in U.S. Pat. No. 4,573,359. A deformation resistant member having point contact engagement with a pipe collar includes a sensor wrapped around the collar in the mid-region of its threaded portion. As the pipe is threaded into the collar, bearing forces exerted on the collar are measured by strain gauges in terms of the extension of the sensor. Temperature sensors responsive to the temperatures of the components generate signals for circuits that are used to compensate for thermal effects, so that more accurate readings are hopefully obtained.
Previous techniques attempting to assess the quality of a tubular connection suffer various drawbacks. Some of these drawbacks relate to the requirement that a mechanical device, such as a strain gauge, be placed in direct contact with a portion of the connection at the end of an oilfield joint. This requirement inherently induces such problems, including wear and tear between parts, calibration difficulties, reduced accuracy exacerbated by placing the device in contact with a rough or uneven portion of the connection, temperature-dependent and pressure-dependent influences on the system, and the time and expense of installing, maintaining, and setting up the system.
A better system and method have long been desired for evaluating the quality of an oilfield tubular threaded connection. The disadvantages of the prior art are overcome by the present invention, and an improved system and method are hereinafter disclosed for verifying the quality of a tubular threaded connection during the make-up operation.